I would not discount Musk. He is an intelligent man and will draw on the expertise of other intelligent people to assess the state of the current art, where it is going, and build to create an up to date fab as an extension of that curve with the latest TSMC equipment = 3-5 years with the assorted lead times.
Remember what he did with rocket science? Threw the billion dollar one hit wonders out the window and created reuseable rockets with a high degree of high end printed metal parts involved. Sure he made a lot of scrap = the cost of progress. Now all the old iron is virtual scrap = reuseable is the path.
